This is the 7 x 50 binocular Dr Caroline Bleeker designed for the Royal Dutch Navy (KM= Koninklijke Marine) at the Zeist factory in the 1950's. It's a superb binocular, even today it can compete with modern high class binoculars. On the left side there is an engraving of the Royal Dutch Navy ( a "K" and a "M" divided by an crowned anchor) and the number cl.nr 575.20.10.53. On the right side you find "Dr. C.E.Bleeker Zeist Ibunox 7 x 50".